Earlier today, I got off a plane and fired up Techmeme to check out the news. The breaking headlines all involved one of my favorite web services, Dropbox, buying one of the most interesting new iPhone apps, the elegant, worth-the-wait Gmail client Mailbox.

Which made me shudder.

More often than not, when a large tech company buys a promising startup which is still ramping up, it's terrible news. What the big company usually wants are the little company's smart and talented people — not whatever they’ve been building. So the startup's existing project often goes into limbo or gets officially axed. The list of examples is long and painful: BumpTop, FriendFeed, Lala, SageTV, Sparrow and many, many more.

I assumed that this Mailbox acquisition was another we-love-it-so-much-we're-going-to-kill-it buyout. Then I read Dropbox's blog post on the news, and calmed down:

Dropbox doesn’t replace your folders or your hard drive: it makes them better. The same is true with Mailbox. It doesn’t replace your email: it makes it better. Whether it’s your Dropbox or your Mailbox, we want to find ways to simplify your life.

We’re all looking forward to making Mailbox even better and getting it into as many people’s hands as possible. There’s so much to do and we’re excited to get started!

Whew. It sounds like Dropbox bought Mailbox because it wants to own Mailbox.

Disclaimer: While I admire many things about Mailbox's interface, I'm not using it as my primary iPhone e-mail app. I find it sluggish, and it can't search a Gmail archive in its entirety. So I use Google's official Gmail app instead. But I've been rooting for Mailbox anyhow — and if Dropbox is good to its word, it could end up being that rare acquired product whose best days came after the acquisition.